It has long been known that a careful preparation of the field is essential to the conditions of growth of various crops and consequently to the obtainable yield and, therefore, a final harrowing and smoothing of the soil surface is frequently effected immediately before seeding for which purpose special flexible tine harrows and so-called rotacrats (crumbler drums) have been developed which should leave the soil surface as smooth as possible and without bigger clods. In this respect it is important that only a superficial layer of suitable depth is being worked by the harrow tines, and not less important is that the depth of processing is as constant as possible so as to obtain also an accurate sowing depth by the following mechanical sowing.
The purpose of the present invention is to provide an implement which in the best way fulfils these conditions.
More particularly, the invention relates to a seed bed preparing flexible tine harrow of the type comprising a main frame to be coupled to a tractor and in which a plurality of harrow sections are individually suspended, each harrow section comprising a set of harrow tines clamped in a tine frame which is adjustably suspended in an intermediate frame towingly connected with the main frame and having wheels or drums rolling on the soil surface.
Such harrows are known in which the intermediate frame solely by its own weight and the weight of the harrow tines and their frame rests on the wheels or drums which may be adjustable in relation to the intermediate frame, the towing connection from the main frame to the intermediate frame (and possibly also the suspension of the tine frame therein) being established by means of chains. Dependent on soil conditions such a seed bed harrow can yield a satisfactory working, but in several cases variations in the resistance to the harrow tines and in the bearing capacity of the soil surface will cause the tine frame to tilt or pitch which makes it impossible to fulfil the requirement of a constant harrowing depth.